1. Field of the Invention
This invention relates to missile aerodynamic surfaces and, more particularly, to providing an improved missile tail fin assembly for developing specific control of missile roll rate under certain flight conditions.
2. Description of the Prior Art
As is well known in the art, flight stability can be provided to a missile launched from a launching device, such as a rocket tube, by imparting a rolling motion thereto, normally in the counterclockwise (looking forward) direction. If the missile rolls too fast, guidance phasing errors can develop. If the missile rolls too slowly, roll-pitch coupling, in addition to phasing errors, can develop. With large angles of attack, however, the roll rate of the missile inherently slows because of aerodynamic damping which increases with increased angles of attack. What is desired is a system that compensates for all or some of the decay and also has minimal impact on cost, fin strength, flutter and aerodynamics associated with the fin assembly.
Most tube launched missiles have tail fin assemblies mounted to the rear of the missile body to provide missile stability during flight. The fins of the assembly are folded over in a manner such that the fins do not interfere with the launching. After launch, the fins are caused to extend outward by unfolding to a normal operating position. Prior art systems have been devised which allow the fins to be mounted to the missile body simply and securely. For example, U.S. Pat. No. 3,117,520 discloses a missile having a fitting formed therein in which a fin can be inserted. The fitting has spaced pins formed therein and the corresponding fin has a number of notches which correspond to the location of the spaced pins. The fitting also has a tapered slot arrangement such that when the fin is inserted into the notches and forced to the rear of the missile, a more secure mating between the fitting and the fin is provided. A locking device is also provided to further secure the fin assembly to the missile.
From the above discussion it can be seen that it would be very efficient from a cost standpoint if a tail fin assembly could be provided that both minimizes the roll rate decay problem described hereinabove and, in addition, functions to securely lock the fin assembly to the missile in the desired attitude for operational control. The present invention involves the modification of an existing missile tail fin assembly to achieve such a result.